The present invention generally relates to absorbent garment and textile manufacturing. In particular, it relates to an apparatus and method for using a variable speed device to apply material to a moving web.
Fabrics, such as textiles, woven materials and nonwoven materials constructed from natural or synthetic fibers, may be processed into garments or other assemblies by feeding them through processing lines. It is often desirable to operate these processing lines non-stop or with few interruptions. In many instances when a product being made in the processing line includes fabric or other sheet-like material, these materials are stored in roll form and fed into the line as a continuously moving web of material. When the roll runs out of fabric, a substitute roll may be spliced into the line with or without interrupting the activity of the line. The web may be processed in any number of ways, such as by folding, pinching, bonding, gluing, compressing, sewing, cutting, and the like. In many cases it is preferred that these operations be performed in the machine direction, that is, done in the direction that the material is moving without interrupting the constant flow of fabric along the line.
In many cases it may desirable to apply an intermittent supply of objects to a continuously moving web or to another intermittent supply of objects. For example, in the case of a diaper or other absorbent garment, it may be desirable to apply discrete units (i.e., objects that are not part of a continuous integral supply of material, or which have been severed from such a supply before being introduced to the continuously moving web) in particular locations on the moving web. In the field of absorbent garment manufacturing, typical discrete units include absorbent cores, transfer layers, adhesive tabs, and the like. In many cases, the units may themselves be formed as a continuous supply web that is severed into discrete units prior to being applied to the continuously moving web. The latter operation is sometimes referred to as a xe2x80x9ccut and placexe2x80x9d operation.
The supply of units may be provided at a greater or slower rate, as measured in terms of a linear feed rate, than the continuously moving web. For example, a moving web may have a linear speed of 100 feet per second (fps), and the supply of units may be provided at a rate of only 10 fps. In still other operations, the units may be stationary when they are supplied. In these operations, it may be desirable to accelerate or decelerate the units to the speed of the moving web prior to depositing them on the web.
Current placing devices are typically operated such that their surface velocity matches either the speed of the units as they are initially supplied, the speed of the moving web, or some intermediate speed. Such a device is disclosed, for example, in commonly assigned U.S. Pat. No. 5,415,716 issued to Kendall on May 16, 1995, which is hereby incorporated by reference in its entirety and in a manner consistent with the present invention. Such devices have certain drawbacks. For example, when the units or the web come into contact with a placing device having a different surface velocity they may be subjected to potentially harmful forces, such as impacts, friction, tension, compression, and the like. The units and the web may also damage one another when they contact each other at different speeds, and the differential speed may complicate the joining of the two.
Other currently available placing devices operate at a variable speed so that the units are picked up at one speed and deposited at another speed. For example, one available device, an eccentric path device, uses a number of arms extending from a central rotating hub. The arms are adapted to extend and contract radially while the hub maintains a constant angular velocity, thereby increasing and decreasing the linear velocity of the end of the arms. Units are picked up at one location, such as when the arms are extended, and deposited at the other location, thereby transferring the units between conveyors having a speed differential between them. Although such eccentric path devices may reduce the incidence of harmful forces on the units and the web, they have several disadvantages. For example eccentric path devices require relatively complex and heavy actuation devices that may be difficult or expensive to produce and maintain. Furthermore, eccentric path devices are typically limited by space constraints and mechanical limitations to operating across a relatively narrow speed differential. Even further, such devices can not be modified to operate with different products or at different speeds without making extensive modifications to the device and possibly to the rest of the manufacturing line, making even slight adjustments expensive and difficult.
These and other devices have been used in the particular context of the absorbent garment manufacturing industry. Absorbent garments, such as diapers, adult incontinence products, feminine care products, and the like, are often manufactured from continuous webs of nonwovens and film material. It is often desirable to produce these garments at as great a rate as possible, and so it is desirable to provide an applicator that can operate efficiently and at a high rate of speed.
It would be desirable to provide an improved method and system for cutting and placing material on a continuously moving web that does not subject the various parts of the assembly to harmful differential surface speeds. It would further be desirable for such a method and system to place units cut from a first web moving at a first speed onto a second web moving at a second speed that is greater or less than the speed of the first web. It would also be desirable for such a system to be easily adapted to operate in different manufacturing lines and to operate at different speeds. It would further be desirable to provide such a method and system at an economical cost. The present invention may be employed to provide these and other benefits.
The features of the invention generally may be achieved by an apparatus for assembling absorbent garments having an applicator that is rotated by a motor. The applicator has one or more heads, each of which is adapted to hold absorbent garment parts. A control device controls the rotation of the motor.
The control device rotates the motor, so that the one or more applicator heads travel at a first speed at a first location to pick up one or more parts moving at approximately the first speed, and travel at a second speed at a second location to deposit the one or more parts onto one or more targets moving at approximately the second speed.
In one embodiment, the applicator may have two heads.
In various embodiments, the heads may have gripping devices on them, such as vacuum grips or mechanical grips, or a combination of gripping devices.
In other embodiments, the motor may be an AC servo motor, and the control device may include an AC servo drive.
In various embodiments, the one or more parts may be grip tabs, absorbent core substrates or absorbent core assemblies, which may be deposited onto tissue layers, absorbent cores, and garment chassis layers. And in further embodiments, the one or more targets may be continuous webs of target material, or a series of discrete target objects.
In various embodiments, the first speed may be greater or less than the second speed. The first speed may be equal to about 3% to about 75% of the second speed, or may be equal to about 10% to about 50% of the second speed, and may be equal to about 20% of the second speed.
In various embodiments, the first speed may be about 20 feet per minute to about 1,000 feet per minute and the second speed may be about 50 feet per minute to about 3,000 feet per minute. In other embodiments, the first speed may about 40 feet per minute to about 650 feet per minute and the second speed may be about 1,000 feet per minute to about 2,000 feet per minute. In still other embodiments, the first speed may be about 65 feet per minute to about 328 feet per minute, and the second speed may be about 1,686 feet per minute.
In still other embodiments, the heads may be equipped with cutting devices to sever parts from a continuous supply web. The heads may also be equipped with bonding devices, such as portions of ultrasonic bonding devices.